Ivy wants to see $20$ birds on her hike. So far, she has seen $8$. How many more birds does she need to see?
Solution: We can solve this problem in two ways: $ \begin{aligned}&8 \text{ birds she saw}\\ +&\underline{ {?} \text{ birds left to see}}\\ =&{20} \text{ birds in total}\end{aligned}$ Or: $ \begin{aligned}&{20} \text{ birds in total}\\ -& \underline{8 \text{ birds she saw}}\\ =&{?} \text{ birds left to see}\end{aligned}$ ${12}$ animals